Anhedonia and Emotional Experience in Schizophrenia: Neural and Behavioral Indicators A R

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Anhedonia and Emotional Experience in
Schizophrenia: Neural and Behavioral Indicators
Erin C. Dowd and Deanna M. Barch
Background: Emotional impairments such as anhedonia are often considered key features of schizophrenia. However, self-report research
suggests that emotional experience in response to affect-eliciting stimuli is intact in schizophrenia. Investigation of neural activity during
emotional experience may help clarify whether symptoms of anhedonia more likely reflect alterations of in-the-moment hedonic experience or impairments in other aspects of goal-directed behavior.
Methods: Forty individuals with DSM-IV-TR schizophrenia or schizoaffective disorder and 32 healthy control subjects underwent functional magnetic
resonance imaging while making valence and arousal ratings in response to emotional pictures, words, and faces. Blood oxygen level-dependent
responses were compared between patients and control subjects and were correlated with questionnaire measures of anhedonia.
Results: Patients showed some evidence of blunted valence but not arousal ratings in response to emotional stimuli compared with control
subjects. Higher anhedonia scores were associated with blunted valence ratings in both groups and fully mediated the group differences in
valence ratings. Functional activity was largely intact in patients, except for regions in right ventral striatum and left putamen, which showed
reduced responses to positive stimuli. Higher anhedonia was associated with reduced activation to positive versus negative stimuli in
bilateral amygdala and right ventral striatum in patients and in bilateral caudate in control subjects.
Conclusions: Increased anhedonia is associated with a reduced experience of valence in both patients and control subjects, and group
differences in experienced valence are likely driven by individual differences in anhedonia. Reduced activation of the striatum and amygdala
may contribute to symptoms of anhedonia by failing to signal the salience of positive events.
Key Words: Affect, anhedonia, emotional experience, fMRI, imaging, schizophrenia
A
nhedonia, or the inability to experience pleasure, is a
long-established feature of schizophrenia (1,2) that significantly impacts functional capacity and is resistant to
treatment (3,4). Surprisingly, however, a growing body of selfreport (5,6) and behavioral (7) data suggests that emotional
experience in schizophrenia is intact. One possible explanation
for this discrepancy is that in schizophrenia, clinical measures of
anhedonia reflect not a deficit in consummatory pleasure but a
deficit in anticipatory pleasure or approach motivation (8 –10).
To investigate this possibility, we asked whether neural activity
during emotional experience is also intact in schizophrenia.
In studying brain responses to affect-eliciting stimuli, several
structures are of particular interest. First, the striatum has been
associated with responses to “rewarding” or pleasurable stimuli
(11–13). Furthermore, reduced ventral striatal activity in response
to positive stimuli has been associated with anhedonia in studies
with both healthy (14) and depressed (15,16) individuals. Most
commonly, the mesolimbic dopamine system and its projections
to the striatum are associated with reward prediction and incentive salience (11,17,18), suggesting that this region is instrumental to anticipatory pleasure and approach motivation. Second,
dorsomedial prefrontal cortex (dmPFC) and orbitofrontal cortex
From the Departments of Psychology (DMB), Psychiatry (DMB), and Radiology (DMB), and the Neuroscience Program (ECD), Washington University, St. Louis, Missouri.
Address correspondence to Erin C. Dowd, B.A., Department of Psychology,
Washington University, Box 1125, One Brookings Drive, St. Louis, MO
63130; E-mail: [email protected]
Received Jul 2, 2009; revised Oct 6, 2009; accepted Oct 8, 2009.
0006-3223/09/$36.00
doi:10.1016/j.biopsych.2009.10.020
(OFC) are active during emotional experience across a wide
range of emotion elicitation studies (19). The dmPFC might be
involved in the introspective evaluation of one’s feelings,
whereas OFC might be involved in establishing the threat or
reward value of a stimulus (20). Third, the amygdala is implicated
in processing survival-salient, arousing stimuli, both negative and
positive (21). Finally, activity in the rostral anterior cingulate
cortex (rACC) has been associated with subjective ratings of
pleasantness (22,23).
A number of studies have suggested that striatal activity during
processing of positive stimuli might be altered in schizophrenia. For
example, unmedicated patients have shown reduced ventral striatal
activation during reward anticipation, which correlated with negative symptom severity (24). In emotion perception studies, patients
failed to modulate nucleus accumbens activation when rating
pleasant versus unpleasant odors (25) and demonstrated reduced
phasic (but enhanced tonic) activity in the ventral striatum to both
positive and aversive stimuli (26).
Studies of activity in dmPFC and OFC during emotional experience in schizophrenia have yielded mixed results. Given evidence
of a dissociation between neural activity patterns during emotional
experience versus emotion perception (27), we focus here on
studies in which participants reported their own experienced emotion. Some of these studies found reduced activation of dmPFC and
OFC during sadness in chronic and first-episode schizophrenia
(28,29). However, other studies failed to find group differences in
these regions in patients (30,31) and relatives (32). Functional
neuroimaging studies of amygdala activation in schizophrenia have
also given mixed results (33). Some emotional experience studies
have shown reductions in amygdala activity in patients compared
with control subjects (28,31), whereas others found no group
differences (29,30). Similarly, most emotion perception studies have
found reduced amygdala activity in response to emotional stimuli in
patients relative to control subjects (28,34 –38) and in paranoid
versus nonparanoid patients (39). However, some studies have
shown increased (40,41) or normal (42,43) amygdala activation. The
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E.C. Dowd and D.M. Barch
disparity in these results might reflect small sample sizes, differences
in stimuli, clinical variation across samples, and the need for a
low-level control condition given that neutral stimuli might elicit
greater limbic activation in patients (44) and their relatives (45) than
in control subjects. In the current study, we aimed to address these
concerns by using a large sample and several types of stimuli, by
conducting individual difference analyses, and by examining the
pattern of responses across several emotional conditions rather than
comparing emotional conditions to a neutral baseline.
This study aimed to address three questions. First, we asked
whether self-reports of emotional experience are intact in patients. In keeping with previous data, we hypothesized that
self-reports would be similar between patients and control
subjects. Second, we asked whether neural activity during emotional experience was similar in patients and control subjects. If
functional magnetic resonance imaging (fMRI) is sensitive to
differences in emotional experience not probed by self-report
measures, we would expect to see differences in functional
activity in regions associated with emotional experience. Third,
we asked whether there was a relationship between questionnaire measures of anhedonia and individual differences in selfreported emotion or its associated neural activity.
Methods and Materials
Participants
Participants were 40 outpatients with DSM-IV-TR schizophrenia
or schizoaffective disorder and 32 healthy community control
subjects. All results reported in the following text remained the same
when schizoaffective patients were excluded (see Methods and
Materials in Supplement 1). Control subjects were excluded if they
had any history of or first-order family member with an Axis I
psychotic disorder or any current mood or anxiety disorder other
than Specific Phobia. Other exclusions included: 1) DSM-IV substance abuse or dependence within 6 months; 2) any medical disorder
that is unstable or severe, would confound the assessment of psychiatric diagnosis, or would make participation unsafe; 3) present or past
head injury with neurological sequelae or causing loss of consciousness; and 4) DSM-IV mental retardation (mild or greater). The demographic and clinical characteristics of both participant groups are
shown in Table 1. Groups were matched on age, parental education,
gender, race, and handedness. All patients were taking antipsychotic
medications, which were stable for least 2 weeks.
Participant diagnoses were based on a Structured Clinical
Interview for DSM-IV-TR (46) and on information from medical
Table 1. Clinical and Demographic Characteristics
Mean (SD)
Age
Education
Highest Parental Education
Gender (% Male)
Race (% Caucasian)
Chapman Social Anhedonia
Chapman Physical Anhedonia
SANS Global Anhedonia
Positive Symptoms
Negative Symptoms
Disorganization Symptoms
Duration of Illness (yrs)
Diagnosis Subtype (%)
Schizoaffective—bipolar
Schizoaffective—depressive
Schizophrenia—undifferentiated
Schizophrenia—residual
Schizophrenia—paranoid
Schizophrenia—disorganized
Medication (% Taking)
Aripiprazole
Clozapine
Ziprasidone
Haloperidal
Iloperidone
Risperidone
Quetiapine
Trifluoperazine
Olanzapine
Average Dose (CPZ Equivalents)
CON
SCZ
t or ␹2
df
p
36.25 (10.85)
15.53 (4.29)
12.76 (2.76)
65.6
53.1
2.35 (2.06)
3.45 (2.99)
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
36.8 (8.99)
13.05 (2.27)
13.35 (3.83)
65
47.5
5.28 (2.17)
7.23 (4.18)
2.68 (1.21)
1.83 (.93)
1.81 (1.37)
1.17 (.80)
17.73 (11.25)
.24
3.15
⫺1.65
.003
.225
⫺5.748
⫺4.253
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
70
70
65
1
1
69
69
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
.82
.002a
.1
.95
.64
.001a
.001a
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
7.5
17.5
42.5
15
15
2.5
22.5
5.0
2.5
5.0
2.5
30.0
17.5
2.5
12.5
452.20 (369.60)
Positive symptoms were the sum of global scores for hallucinations and delusions; negative symptoms were the
sum of global scores for alogia, anhedonia, avolition, affective flattening, and attentional impairment; and disorganization symptoms were the sum of global scores for bizarre behavior, positive thought disorder, and inappropriate
affect.
CON, control; SCZ, schizophrenia; SANS, scale for the assessment of negative symptoms; CPZ, chlorpromazine.
a
p ⬍ .05.
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E.C. Dowd and D.M. Barch
records and corroborative sources. Clinical symptoms were rated
with the Scales for the Assessment of Positive Symptoms (SAPS)
(47) and Negative Symptoms (SANS) (48). We assessed anhedonia symptoms with the SANS global anhedonia score and the
self-report Chapman physical and social anhedonia scales (49)
and handedness with the Edinburgh Index (50). See Methods
and Materials in Supplement 1 for details.
Materials and Tasks
All participants were scanned while making valence and
arousal ratings of their own subjective responses to emotional
pictures, words, and faces. Valence (pleasant– unpleasant) and
arousal (activation– deactivation) are independent dimensions of
affect (51) that are considered vital features of emotional experience (20). Participants rated their experience of each stimulus
by button press as positive, negative, or neutral during valence
runs or as highly, slightly, or not aroused during arousal runs.
Stimuli consisted of 50 each emotional words, pictures, and
faces, 10 in each of the following categories: negative high
arousal (NHA), negative low arousal (NLA), positive high arousal
(PHA), positive low arousal (PLA), and neutral (NEU); see
Methods and Materials in Supplement 1. Participants performed
the task for six runs; one run each of arousal and valence
judgments for each stimulus type (pictures, words, faces). Stimuli
were presented for 2000 msec with a jittered interstimulus
interval varying from 1000 to 10,000 msec.
Behavioral Data Analysis
Valence and Arousal Ratings. We analyzed the valence and
arousal ratings with repeated measures analyses of variance with
group (schizophrenia, control) as a between-subjects factor and
stimulus (picture, word, face) and condition (NHA, NLA, NEU,
PLA, PHA) as within-subjects factors. To further characterize the
pattern of responses as a function of condition, we created a
priori contrasts that were sensitive to the valence and/or arousal
characteristics of the stimuli. To examine the effect of valence
irrespective of arousal, we used a linear contrast with weights of
⫺1, ⫺1, 0, 1, and 1 for NHA, NLA, NEU, PLA, and PHA,
respectively (valence contrast). To examine the effect of arousal
irrespective of valence, we used a quadratic contrast with
weights of 2, ⫺1, ⫺2, ⫺1, and 2 for NHA, NLA, NEU, PLA, and
PHA, respectively (arousal contrast). To examine whether the
valence ratings were influenced by both the valence and arousal
characteristics of the stimuli, we also created a linear contrast in
which valence was amplified by arousal, with weights of ⫺2, ⫺1,
0, 1, and 2, for NHA, NLA, NEU, PLA, and PHA, respectively
(valence ⫻ arousal contrast). We tested the significance of these
contrasts with univariate F tests within each group.
Individual Difference Analyses. We conducted linear regression analyses to examine the extent to which anhedonia
scores predicted valence ratings within each group. To determine whether the relationship between valence ratings in response to PHA/NHA stimuli and Chapman Physical/Social Anhedonia scores differed between groups, we conducted hierarchical
regression analyses with anhedonia score (physical or social) and
group entered in Step 1 and group ⫻ anhedonia interaction
entered in Step 2. We also examined whether anhedonia scores
mediated the effect of group on valence ratings. To do this, we
conducted two separate multiple mediation analyses with a
Sobel procedure with bootstrapping (52), with PHA or NHA
valence ratings as the dependent variable, group as the independent variable, and physical and social anhedonia scores as
mediators. Within the patient group, we also conducted correla-
BIOL PSYCHIATRY 2009;xx:xxx 3
tions between PHA/NHA valence ratings and SANS global anhedonia, and with SANS avolition, alogia, and affective flattening to
examine the specificity to anhedonia.
fMRI Analysis
For fMRI acquisition and image analysis, see Methods and
Materials in Supplement 1. Functional activation was analyzed
with the valence, arousal, and valence ⫻ arousal contrasts in
both region of interest (ROI) and whole-brain analyses. We
examined voxelwise t tests at the group level within predefined
ROI masks, including the amygdala, striatum, dmPFC, OFC, and
rACC (Methods and Materials in Supplement 1). Both the wholebrain and ROI analyses were corrected for multiple comparisons
with combined p value/cluster size thresholds, determined with
Monte Carlo simulations to provide an overall false-positive rate
of .05 (53,54). These thresholds were p ⬍ .01 and 14 voxels for
ROI analyses and p ⬍ .003 and 30 voxels for whole-brain
analyses. To identify regions whose activation patterns were
consistent with the valence and arousal patterns of interest, we
first conducted one-sample t tests for each contrast on both
groups combined. To identify regions showing group differences
in activation, we also performed group t tests on each contrast. In
both analyses, significant regions were followed up with simple
effects tests to determine the activation pattern within each group
separately. To examine individual differences in functional ac-
Figure 1. Valence and arousal ratings as a function of condition in individuals with schizophrenia (SCZ) and control subjects (CON). (A) Average valence ratings (1 ⫽ negative, 2 ⫽ neutral, 3 ⫽ positive) collapsed across
stimulus type (pictures, words, faces) for each emotional condition: negative
high arousal (NHA), negative low arousal (NLA), neutral (NEU), positive low
arousal (PLA), and positive high arousal (PHA). (B) Average arousal ratings
(1 ⫽ highly aroused, 2 ⫽ slightly aroused, 3 ⫽ not aroused) collapsed across
stimulus type (pictures, words, faces) for each emotional condition. *p ⬍ .05.
Error bars represent standard error.
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Table 2. Hierarchical Regression Analyses with Group and Anhedonia Scores to Predict Valence Ratings
Dependent Variable
PHA Valence Rating
PHA Valence Rating
NHA Valence Rating
NHA Valence Rating
Predictors
Step 1
Group
Physical anhedonia
Step 2
Group ⫻ physical anhedonia
Step 1
Group
Social Anhedonia
Step 2
Group ⫻ social anhedonia
Step 1
Group
Physical anhedonia
Step 2
Group ⫻ physical anhedonia
Step 1
Group
Social anhedonia
Step 2
Group ⫻ social anhedonia
R2
R2 Change
␤
.229a
⫺.191
⫺.360b
.231b
.002
⫺.127
.192b
⫺.177
⫺.313d
.206b
.014
⫺.357
.199b
.191
.326c
.205b
.006
⫺.219
.190b
.151
.332d
.197c
.007
⫺.246
PHA, positive high arousal; NHA, negative high arousal.
p ⬍ .001.
b
p ⬍ .005.
c
p ⬍ .01.
d
p ⬍ .05.
a
tivity, we also conducted voxelwise correlation analyses between
contrast scores and anhedonia scores. Correlations were conducted within each group separately, and correlation coefficients
were compared between groups with Fisher r-to-z transformations.
Results
Behavioral Results
Anhedonia Scores. Overall, individuals with schizophrenia
had higher anhedonia scores than control subjects on both
Chapman scales (Table 1).
Valence and Arousal Ratings. For valence (Figure 1A), there
was a significant main effect of condition [F (4,280) ⫽ 659.85, p ⬍
.001] and significant group ⫻ condition [F (4,280) ⫽ 13.49, p ⬍
.001] and stimulus ⫻ condition [F (8,560) ⫽ 12.70, p ⬍ .001]
interactions. Simple effects tests revealed significant effects of
condition for control subjects [F (4,280) ⫽ 386.85, p ⬍ .001] and
patients [F (4,280) ⫽ 273.95, p ⬍ .001]. However, comparisons
within each condition revealed that patients’ responses to negative stimuli were less negative [F (1,70) ⫽ 9.62, p ⬍ .004 for NHA;
F (1,70) ⫽ 7.87, p ⬍ .007 for NLA] and responses to positive
stimuli were less positive [F (1,70) ⫽ 15.77, p ⬍ .001 for PLA,
Figure 2. Scatterplots of (A) average valence ratings to
PHA stimuli as a function of Chapman physical anhedonia, (B) average valence ratings to PHA stimuli as a function of Chapman social anhedonia, (C) average valence
ratings to NHA stimuli as a function of Chapman physical
anhedonia, and (D) average valence ratings to NHA stimuli as a function of Chapman social anhedonia, in individuals with SCZ (circles) and CON (triangles). Abbreviations
as in Figure 1.
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—
28, ⫺10, ⫺15
ROI, region of interest; BA, Brodmann area; CON, control; SCZ, schizophrenia; R, Right; OFC, orbitofrontal cortex; neu, neutral; neg, negative; pos, positive; rACC, rostral anterior cingulate cortex; ha, high
arousal; la, low arousal; dmPFC, dorsomedial prefrontal cortex; nha, negative high arousal; nla, negative low arousal.
a
p ⬍ .001.
b
p ⬍ .005.
c
p ⬍ .01.
d
p ⬍ .05.
c
d
NS
NS
NS
nha ⬎ nla ⫽ neu
neg ⬎ neu ⫽ pos
⫺3.41
NS
—
9
21
d
b
NS
NS
NS
NS
NS
NS
ha ⬎ la ⫽ neu
ha ⬎ la ⫽ neu
—
—
3.39
3.68
c
a
26, ⫺14, ⫺8
⫺1, 51, 23
24
79
b
b
NS
NS
NS
NS
b
NS
—
—
neu ⬎ neg ⬎ pos
deactivation: neu ⫽ neg ⬎ pos
⫺3.98
4.61
27
17
47
32
41, 24, ⫺4
1, 35, 3
Valence Contrast
R OFC
rACC
Arousal Contrast
R amygdala
dmPFC
Valence ⫻ Arousal
Contrast
R amygdala
Within SCZ
Contrast
Within CON
Contrast
Group Difference
in Contrast
Group ⫻ Condition
Interaction
Valence
Brain Region
Talairach
Coordinates
BA
Number
Voxels
Z
Activation Pattern
Arousal
Main Effect
of Group
Regional Analyses
F (1,70) ⫽ 9.75, p ⬍ .004 for PHA] than control subjects. Both the
valence and valence ⫻ arousal contrasts were significant for both
groups, with similar effect sizes [valence contrast: F (1,70) ⫽
521.50, p ⬍ .001, ␩p2 ⫽ .882 for control subjects, F (1,70) ⫽
368.23, p ⬍ .001, ␩p2 ⫽ .840 for patients; valence ⫻ arousal
contrast: F (1,70) ⫽ 509.33, p ⬍ .001, ␩p2 ⫽ .879 for control
subjects; F (1,70) ⫽ 364.80, p ⬍ .001, ␩p2 ⫽ .839 for patients].
Because stimulus type (picture, word, face) did not interact with
group in any of our analyses (behavioral or fMRI), stimulus
effects are not discussed further here (but see Results in Supplement 1).
For the arousal ratings (Figure 1B), there were significant
main effects of stimulus [F (2,140) ⫽ 23.41, p ⬍ .001] and
condition [F (4,280) ⫽ 55.96, p ⬍ .001] and significant stimulus ⫻
condition [F (8,560) ⫽ 5.03, p ⬍ .001] and group ⫻ condition
[F (4,280) ⫽ 3.15, p ⬍ .009] interactions. Simple effects tests
Table 3. Results of ROI Analyses of Valence, Arousal, and Valence ⫻ Arousal Contrasts in the Total Sample
Figure 3. Results of region of interest analyses of valence, arousal, and
valence ⫻ arousal contrasts in the total sample (both patients and control
subjects). Regions are described in Table 3. Images are shown in neurological orientation. (A) Regions showing significant activation in the valence
contrast. Positive z scores (red) indicate greater activation to positively
valenced stimuli than to negatively valenced stimuli; negative z scores
(blue) indicate greater activation to negatively valenced stimuli than to
positively valenced stimuli. (B) Regions showing significant activation in the
arousal contrast. Positive z scores (red) indicate greater activation to high
arousal stimuli relative to neutral and low-arousal stimuli. (C) Regions showing significant activation in the valence-by-arousal contrast. Negative z
scores indicate greater activation to negative high arousal stimuli than to
positive and/or low-arousal stimuli.
b
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Figure 4. Results of region of interest analyses of group t tests
between patients and control subjects for the valence and
valence ⫻ arousal contrasts. Regions are described in Table 4.
Images are shown in neurological orientation. (A) Right ventral striatal region demonstrating a group difference in the
valence contrast. Activation did not differ significantly in the
NHA, NLA, or NEU conditions but was significantly lower in
patients than in control subjects for the PLA and PHA conditions. (B) Left putamen region demonstrating a group difference in the valence ⫻ arousal contrast. Activation did not
differ significantly in the negative, neutral, or PLA conditions
but was significantly lower in patients than in control subjects
in the PHA condition. *p ⬍ .05. Error bars represent standard
error. Abbreviations as in Figure 1.
revealed significant effects of condition within each group
[F (4,280) ⫽ 39.35, p ⬍ .001 for control subjects, F (4,280) ⫽
17.72, p ⬍ .001 for patients]. Furthermore, group comparisons
within each condition revealed a significant group difference
only for the NEU condition: compared with control subjects,
patients showed higher arousal in response to neutral stimuli
[F (1,70) ⫽ 6.87, p ⬍ .02]. The arousal contrast was significant for
both groups [F (1,70) ⫽ 151.45, p ⬍ .001, ␩p2 ⫽ .654 for control
subjects; F (1,70) ⫽ 68.76, p ⬍ .001, ␩p2 ⫽ .496 for patients].
Taken together, these results indicate that patients showed
blunted valence ratings in response to emotional stimuli. However, the patterns of both valence and arousal ratings as a
function of emotional condition were similar between groups.
Individual Difference Analyses. We conducted hierarchical
regression analyses with Chapman anhedonia scores predicting
valence ratings to PHA and NHA stimuli in patients and control
subjects (Table 2). In all of these analyses, anhedonia score and
group accounted for a significant portion of the variance in the
valence ratings, and adding a group ⫻ anhedonia interaction
term failed to account for significantly more variance. As expected, higher physical and social anhedonia scores were associated with less-positive responses to PHA stimuli and lessTable 4. Results of ROI Analyses of Group t Tests Between Patients and
Control Subjects for the Valence and Valence ⫻ Arousal Contrasts
Brain Region
valence contrast
R ventral striatum
Valence ⫻ Arousal Contrast
L putamen
Talairach
Coordinates
Number
Voxels
Z
7, 3, ⫺4
14
2.80
⫺28, ⫺14, ⫺1
17
3.44
ROI, region of interest; R, Right; L, Left.
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negative responses to NHA stimuli in both groups (Figure 2).
Similarly, within the patient group, SANS anhedonia correlated
negatively with PHA valence ratings (r ⫽ ⫺.37, p ⬍ .03),
although it failed to correlate with NHA valence ratings (p ⬎ .16).
Together, these results suggest that, within both patients and
control subjects, higher levels of anhedonia are associated with
less-valenced experiences of emotional stimuli.
Multiple mediation analyses revealed that for both PHA and
NHA valence ratings, the effect of group was fully mediated by
physical and social anhedonia scores [effect of group on valence
rating, controlling for physical and social anhedonia: t (69) ⫽
⫺1.2, p ⬎ .24 for PHA, t (69) ⫽ 1.0, p ⬎ .31 for NHA]. The total
mediated effect was significant in both models (95% confidence
interval: ⫺.27, ⫺.01 for PHA; .02, .25 for NHA). For PHA ratings,
only physical anhedonia was significant as a specific mediator
(95% confidence interval: ⫺.16, ⫺.003), and for NHA ratings,
neither specific mediator was significant alone.
To evaluate the specificity of these results to anhedonia, we
correlated PHA and NHA valence ratings with SANS global
avolition, alogia, and affective flattening in patients and found
that avolition also correlated negatively with PHA valence ratings
(r ⫽ ⫺.34, p ⬍ .04) and positively with NHA valence ratings (r ⫽
.36, p ⬍ .03). Aside from a trend-level correlation between alogia
and NHA ratings (r ⫽ .30, p ⬍ .07), alogia and affective flattening
failed to correlate with either measure (p ⬎ .16). Therefore, a
reduced experience of positive and negative emotion seems to
be related to symptoms of anhedonia and amotivation but not to
other negative emotional symptoms.
fMRI Results
ROI Analyses: One-Sample t Tests. As shown in Figure 3,
one-sample t tests identified several regions within the ROIs with
activity patterns significant for the valence, arousal, and valence ⫻
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E.C. Dowd and D.M. Barch
Figure 5. Results of whole-brain analyses of valence, arousal, and valence ⫻ arousal contrasts in the total sample (both patients and control subjects). Regions
are described in Table S5 in Supplement 1. Images are shown in neurological orientation. (A) Regions showing significant activation in the valence contrast.
Positive z scores (red) indicate greater activation to positively valenced stimuli than to negatively valenced stimuli; negative z scores (blue) indicate greater
activation to negatively valenced stimuli than to positively valenced stimuli. (B) Regions showing significant activation in the arousal contrast. Positive z scores
(red) indicate greater activation to high arousal stimuli relative to neutral and low-arousal stimuli; negative z scores (blue) indicate greater activation to neutral
and low-arousal stimuli than to high-arousal stimuli. (C) Regions showing significant activation in the valence ⫻ arousal contrast. Negative z scores indicate
greater activation to negative high arousal stimuli than to positive and/or low-arousal stimuli.
arousal contrasts. These regions and their activation patterns are
detailed in Table 3.
Group t Tests. One region in right ventral striatum demonstrated a significant group difference in the valence contrast, and
one in left putamen showed a group difference in the valence ⫻
arousal contrast (Figure 4, Table 4). As shown in Figure 4, in both
of these regions, patients showed reduced activation compared
with control subjects for the positive conditions. Post hoc tests
revealed that, in left putamen, PHA activation differed significantly between groups [F (1,70) ⫽ 5.05, p ⬍ .04]. In right
ventral striatum, there were significant group differences in
both PHA [F (1.70) ⫽ 5.58, p ⬍ .03] and PLA [F (1.70) ⫽ 6.14,
p ⬍ .03].
Whole-Brain Analyses
As shown in Figure 5 (and Table S5 in Supplement 1), a
number of regions were identified by the valence, arousal, and
valence ⫻ arousal contrasts in whole-brain one-sample t tests. In
the group t tests, however, we did not find a single region that
showed a significant group difference in any of the contrasts. To
further examine whether the activity patterns were similar between groups, we conducted follow-up group analyses on each
region identified in the one-sample t tests. As shown in Table S5
in Supplement 1, overall activity differed between patients and
control subjects in a number of these regions. However: 1) in
every region, both patients and control subjects showed signifi-
cant within-group effects of the relevant contrast; 2) in every
region, there were no significant group differences in the magnitude of the contrast; and 3) in all but two regions, the pattern
as a function of emotional condition was the same for both
patients and control subjects. Thus, outside of the striatum,
patients and control subjects demonstrated similar neural responses to both valence and arousal.
Individual Difference Analyses. We first conducted correlations between anhedonia scores and average activation contrast
scores within the regions showing group differences in the
contrasts. This analysis revealed a negative correlation between
physical anhedonia and valence ⫻ arousal contrast score in the
right ventral striatum in patients (r ⫽ ⫺.36, p ⬍ .04), indicating
that patients with higher anhedonia scores showed less activation in this region in response to positive stimuli compared with
neutral and negative stimuli. This correlation was not significant
in control subjects (r ⫽ ⫺.17, p ⬎ .34), although the group
difference in correlation coefficients was not significant (p ⬎ .77).
We next conducted voxelwise ROI analyses (Table 5), in which
physical anhedonia correlated negatively with the valence contrast in left amygdala and with the valence ⫻ arousal contrast in
right amygdala in patients. In control subjects, social anhedonia
correlated negatively with the valence contrast in bilateral caudate. Comparison of correlation coefficients between groups
revealed a significant difference in the right caudate (p ⬍ .02)
Table 5. ROI Results of Correlation Analyses Between Anhedonia Scores and fMRI Valence and Valence ⫻ Arousal Contrast Scores
Contrast
Anhedonia Measure
Talairach Coordinates
Region Name
Number Voxels
r
Z
Control
Valence
Chapman social anhedonia
8, ⫺1, 14
⫺13, ⫺2, 18
R caudate
L caudate
14
28
⫺.550
⫺.539
⫺3.26
⫺3.18
Schizophrenia
Valence
Valence ⫻ Arousal
Chapman physical anhedonia
Chapman physical anhedonia
⫺14, ⫺9, ⫺15
17, ⫺14, ⫺11
L amygdala
R amygdala
17
15
⫺.446
⫺.413
⫺2.89
⫺2.58
ROI, region of interest; fMRI, functional magnetic resonance imaging; R, Right; L, Left.
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ARTICLE IN PRESS
8 BIOL PSYCHIATRY 2009;xx:xxx
and a trend level difference in left caudate (p ⬍ .08) but no
difference in either amygdala region (p ⬎ .70).
Discussion
Behavioral Measures of Emotional Experience
We found that individuals with schizophrenia self-reported
more anhedonia than control subjects, in agreement with most
clinical data. Behaviorally, there was a group ⫻ condition
interaction in the valence ratings, and post hoc tests revealed that
patients rated their experience of the valenced stimuli as less
valenced than control subjects. This finding is at odds with most
studies, which have shown intact responses to emotional stimuli.
However, although the arousal ratings also showed a group ⫻
condition interaction, the only post hoc group difference was
heightened arousal ratings in response to neutral stimuli in
patients. This finding suggests that patients’ experience of
arousal in response to emotional stimuli is intact, in agreement
with previous literature. Furthermore, patients clearly showed
modulation of both valence and arousal ratings as a function of
the emotional content of the stimuli: when we conducted
contrast analyses sensitive to valence, arousal, and valence ⫻
arousal interaction, the relevant contrasts were significant within
both groups, with similar effect sizes. Overall, although these
findings suggest that the range of experienced emotion might be
narrowed in patients, they also show that evoked arousal is
relatively intact and that affective stimuli modulate emotional
experience in similar ways in patients and control subjects.
Individual difference analyses revealed that higher anhedonia
was associated with blunted responses to emotional stimuli
within both patients and control subjects. Furthermore, the group
differences in valence ratings were fully mediated by anhedonia
scores. Together, these results indicate that the level of anhedonia rather than simply the diagnosis of schizophrenia might
underlie the blunted responses to emotional stimuli seen in
patients. This finding highlights the importance of including
sufficiently powered individual difference analyses in future
work.
fMRI Measures of Emotion-Processing
The fMRI analysis revealed that brain activity is largely intact
during emotional experience in schizophrenia. On whole-brain
analysis, we did not find any regions that showed group differences in any contrast, suggesting similar patterns of neural
activity in patients and control subjects. On ROI analysis, however, right ventral striatum and left putamen showed reduced
activation to positive stimuli in patients compared with control
subjects. Given past research showing that striatal activation is
associated with the anticipation (55) and receipt (23) of pleasurable stimuli, this finding might represent a failure to respond to
positive experiences that contributes to an inability to anticipate
or want such experiences in the future (56).
In support of this interpretation, reduced activation to positive
versus negative stimuli in the same ventral striatal region was also
associated with higher physical anhedonia in patients. This
finding suggests that the group differences in activation seen in
this region might be driven by individual differences in anhedonia. Similarly, bilateral amygdala activation to positive versus
negative stimuli was reduced in patients who were higher in
physical anhedonia. Within control subjects, greater social anhedonia was associated with decreased bilateral caudate activation
in response to positive relative to negative stimuli. Because the
amygdala (21) and striatum (57) are thought to be involved in
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E.C. Dowd and D.M. Barch
salience attribution, these results might indicate that these regions fail to mark positive events as salient in anhedonic
individuals, leading to a blunted experience of emotion and a
reduced ability to seek out similar events in the future.
Given that the ventral striatum is typically associated with
reward processing, it is interesting to speculate on how these
results relate to findings of reduced ventral striatal activation
during reward anticipation in schizophrenia (24). Notably, the
reduced ventral striatal activation to positive stimuli seen here in
patients might represent a deficit in motivational or rewardprediction processes rather than in hedonic processes per se.
During learning, dopaminergic neurons initially fire to unexpected positive stimuli, shifting over time to fire to cues that
predict these rewards (18). Thus, the deficient right ventral
striatal activation reported here could reflect a failure of this
initial dopaminergic firing to unpredicted positive stimuli, potentially impairing reward prediction/incentive salience and leading
to reduced anticipatory activation. Importantly, this impairment
in predictive or motivational processes might be independent of
the hedonic response to the reward, allowing a normal experience of “liking” combined with reduced “wanting.” This is
consistent with the view that consummatory pleasure is intact in
schizophrenia while anticipatory pleasure is impaired (10).
Given the finding of group differences in striatal activity, a
major limitation of this study is that all patients were taking
medications that block dopamine receptors, potentially altering
striatal function. However, most patients were taking atypical
antipsychotics, which have a lesser effect on striatal activity
during reward processing than typical antipsychotics (58,59).
Furthermore, when we removed from analysis all patients taking
typical antipsychotics or risperidone (which are pharmacologically similar), the group differences and correlations remained
significant. In addition, neural activity did not correlate with
antipsychotic dose within the regions showing group differences
(Results in Supplement 1). Although the possibility of medication
effects cannot be ruled out without examination of unmedicated
patients, we feel that these results provide reasonable evidence
that the findings reported here were not driven by medications.
In summary, this study makes several important contributions
to the literature on emotional experience and its related brain
activity in schizophrenia. First, although patients showed blunted
responses to emotional stimuli compared with control subjects,
these group differences in ratings were clearly mediated by the
level of anhedonia displayed by the participants. Second, the
pattern of brain activity in response to emotional stimuli was
largely intact, with the exception of two striatal regions that
showed reduced responses to positive stimuli. Third, blunted
activation to positive versus negative stimuli correlated with
anhedonia in the amygdala and right ventral striatum in patients
and in the caudate in control subjects, suggesting that failure to
mark stimuli as salient or rewarding might contribute to symptoms of anhedonia. Clinically, these results highlight the importance of individual differences, suggesting that optimal treatment
strategies are best tailored to the individual symptomatology of
the patient. Future work examining the relationship between
reduced neural responses to positive stimuli and deficits in
motivated behavior, with paradigms that probe for reward
anticipation and reinforcement learning in anhedonic individuals, might shed additional light on the questions raised here.
This research was supported by a National Institutes of Health
Grant R01MH06603101 as well as the Conte Center for the
Neuroscience of Mental Disorders Grant MH071616 awarded to
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E.C. Dowd and D.M. Barch
DMB. We thank Naomi Yodkovik and Lisa Dickman for help with
data acquisition and processing.
The authors report no biomedical financial interests or potential conflicts of interest.
26.
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